Pressure sensor devices which include microelectromechanical system (MEMS) chips are used as implants, for example, as an implantable cardiac device which may be implanted in a patient to improve the function of the patient's heart. Such MEMS chips can have dimensions of less than 1 mm by 1 mm by 0.3 mm, and can deliver precise pressure measurements with an accuracy of 2 mbar or less.
For usage in a reactive medium such as blood, MEMS chips are usually embedded in an inert liquid and hermetically sealed against the reactive medium for protection of the chips. Typical constructions use metallic housings having a window covered with a pressure transmitting membrane. For medical implants, titanium is usually chosen because of its biocompatibility and long-time stability. The MEMS chip is arranged in an incompressible and inert liquid, such as oil, inside the housing. A typical thickness of the housing is more than 100 μm and the window with the pressure transmitting membrane is arranged at a front face of the housing (see U.S. Pat. No. 8,142,362), or in the wall of the housing (see U.S. Pat. No. 8,573,062).